Cytokine gene expression in splenic CD4(+) and CD8(+) T-cell subsets of chickens infected with Marek's disease virus.

Specific-pathogen free chickens were infected with the RB1B strain of Marek's disease virus (MDV) and T cells from the spleens of infected as well as age-matched controls were fractionated by flow cytometry at 4, 10, and 21 days post-infection (d.p.i.). Real-time quantitative reverse transcription PCR was used to assess the amount of cytokine transcripts as well as viral genes meq and glycoprotein B (gB). There was an increase in the number of CD4(+) T cells, as well as a significant increase in the expression of the viral meq gene in CD4(+) T cells, which coincided with the presence of tumors in various organs of infected birds. It was also observed that there was a significant upregulation in the amount of the gene expression of interferon (IFN)-gamma, interleukin (IL)-18, and IL-6 at 4 and 21 d.p.i. in CD4(+) and CD8(+) T-cell subsets. The expression of IL-10 was upregulated as well. The outcome of the cytokine milieu inclined towards the induction of a type I immune response at 4 and 21 d.p.i. Our study indicates that MDV-associated cytokine profiles vary in CD4(+) and CD8(+) T-cell subsets, and that cytokines including IFN-gamma, IL-18, IL-6, and IL-10 may play a role in the elicitation of an immune response to MDV.